Semiconductor device and method for producing the same, and anisotropic conductive circuit board

ABSTRACT

A semiconductor device includes a circuit board, a semiconductor element that is mounted on an upper surface of the circuit board and has an electrode terminal, and a sealing resin for sealing a periphery of the semiconductor element that is mounted on the upper surface of the circuit board. The circuit board includes a plurality of conductive members and an insulating substance for binding and fixing the plurality of conductive members. Each of the plurality of conductive members includes a conductive material formed integrally from the upper surface through the lower surface of the circuit board, and an insulating material covering an outer circumference of the conductive material. The conductive material of at least one conductive member of the plurality of conductive members is exposed to the upper surface of the circuit board. The electrode terminal of the semiconductor element is electrically connected to the conductive material of the conductive member exposed to the upper surface of the circuit board via a connecting member.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a semiconductor device and amethod for producing the same, and an anisotropic conductive circuitboard. In particular, the present invention relates to a semiconductordevice employing a circuit board including a bonding pad portion onwhich a semiconductor element is to be mounted on its upper surface andelectrode pads connected to electrode terminals of the semiconductorelement via a connecting member, and a method for producing such asemiconductor device, and relates to a semiconductor device having goodelectrical and thermal characteristics and a method for producing such asemiconductor device.

[0002] Hereinafter, a semiconductor device employing a commonly usedprinted circuit board used as a component of a semiconductor packagewill be described.

[0003]FIGS. 8A to 8E are views illustrating the production process of aconventional LGA (lard grid array) type semiconductor device in theorder of the production. FIG. 8A is a plan view, FIGS. 8B to 8E arecross-sectional views of a relevant part taken along line A-A1 of FIG.8A.

[0004] First, to produce a printed circuit board as shown in FIG. 8A, aninsulating substrate 2 to which copper foils having a thickness of 6 to35 μm are attached to its upper and lower surfaces is prepared. Thisinsulating substrate 2 is a substrate in which glass fabrics have beenincorporated into an epoxy resin.

[0005] Next, via holes are formed having a predetermine diameter inpredetermined positions of the insulating substrate with a drill or alaser. Then, thick copper films are formed on the side walls of theformed via holes by electroless plating or electrolytic plating. At thispoint, the copper foils on the upper and the lower surfaces of theinsulating substrate are connected by the thick copper films.

[0006] Next, dry films are attached onto the surfaces of the copperfoils on the upper and the lower surfaces of the insulating substrate byheating and pressing. The dry films are made of a material that causes areaction with respect to light having a specific wavelength, and thesurfaces of the dry films are irradiated with light having a wavelengthfor a reaction via a photomask on which a predetermined circuit patternhas been formed. Thereafter, in the circuit pattern formed on the dryfilms on the copper foil surface on the upper and the lower surfaces ofthe insulating substrate, the portions to be removed of the dry filmsare dissolved with a developer and removed after exposure to the light.Then, after the removal, the dry films are heated or irradiated withultraviolet rays so that the remaining portions of the dry films arecured. Using these dry films as masks, exposed copper film portion isremoved by allowing the copper foil erosion chemicals such as nitricacid, sulfuric acid or hydrochloric acid to be in contact with thesurface of the copper foils, for example, by dipping or spraying.

[0007] Finally, the dry films that have been exposed to the chemicalsand cured are removed by using a detaching agent, dissolving it inoxygen plasma, or converting it to carbon dioxide. Solder resist filmsare formed on the upper and the lower surfaces of the thus obtainedprinted circuit board 1 by screen printing, and the pattern is formed onthe solder resist film via a photomask by an exposure machine. Then, theportion to be dissolved of the solder resist film is dissolved with adeveloper and removed, and then heated and cured. Then, nickel and goldare deposited in this order in predetermined thicknesses by electrolyticplating on the surface of the copper foil portion corresponding to theopening of the pattern from which the solder resist film is removed.Thereafter, the printed circuit board is divided so as to form a frameshape or divided into individual segments by stamping with a pressingmachine or a cutting machine.

[0008] The printed circuit board 1 for use in a conventional boardstructure package, which includes bonding pads, electrode pads, andthrough-holes connecting the bonding pads and the electrode pads on theupper surface to those on the lower surface, has been produced in thismanner.

[0009] As shown in FIG. 8A, on each of the upper and the lower surfacesof the insulating substrate 2, the produced printed circuit board 1includes a bonding pad 3, electrode pads 4 and through-holes 6connecting the pads 3 and 4 on the upper surface to the correspondingpads on the lower surface. The surface of each of the pads on theprinted circuit board 1 is coated with a thin film made of gold orsilver. The bonding pad 3 consists of the upper bonding pad and thelower bonding pad, and the electrode pad 4 consists of the upperelectrode pad and the lower electrode pad. A solder resist film 5 isformed on the substrate in such a manner that the pads 3 and 4 areexposed.

[0010] Next, referring to 8A to 8E, a method for producing asemiconductor device (for a LGA type package) including the printedcircuit board 1 will be described below.

[0011] First, the circuit board 1 as shown in FIG. 8A is prepared. Inthe prepared circuit board 1, as shown in FIG. 8B, an upper bonding pad3 a, a lower bonding pad 3 b, upper electrode pads 4 a, and lowerelectrode pads 4 b are formed on an insulating substrate 2, andthrough-holes 6 for connecting the bonding pads 3 a and 3 b and theelectrode pads 4 a and 4 b on the upper surface of the substrate to thecorresponding pads on the lower surface are provided.

[0012] Then, as shown in FIG. 8C, a die bonding process is performed, inwhich a semiconductor element 7 is attached onto the upper bonding pad 3a with a conductive adhesive 8 such as silver paste, and then heating isperformed at 150° C. for one hour in the air for strong adhesion.

[0013] Then, as shown in FIG. 8D, a wire bonding process is performed,in which electrode terminals (not shown) on the semiconductor element 7mounted on the substrate are connected to the upper electrode pads 4 awith connecting members 9 such as metal fine lines (wires) using a wirebonder. This connection is performed under the following conditions: Theheating temperature of the printed circuit board 1 is 200° C., the loadfor connection between the connecting members 9 and the electrodeterminals of the semiconductor element 7 is 20 gf, and the load forconnection between the connecting members 9 and the upper electrode pads4 a on the printed circuit board 1 is 100 gf. This connection isperformed using ultrasonic vibration as well.

[0014] Next, as shown in FIG. 8E, an outline molding process isperformed, in which a sealing resin 10 is molded to a predeterminedpackage outline with a transfer mold or a print sealing so that thesemiconductor element 7 and the connecting members 9 provided on theupper surface of the printed circuit board 1 are sealed and formed intoone piece.

[0015] In this manner, a semiconductor device for an LGA type packageincluding a conventionally commonly used printed circuit board as acomponent is produced. Furthermore, if metal ball terminals are providedon the lower electrode pads 4 b (land portions) on the bottom surface ofthe printed circuit board 1, a BGA (ball grid array) type semiconductorpackage can be achieved.

[0016] However, the conventional semiconductor device has the followingproblems. In the conventional printed circuit board type packageincluding a glass epoxy substrate, the connection between the upperelectrode pads and the lower electrode pads or the connection betweenthe upper bonding pad and the lower bonding pad are established via thevia holes, so that variations in the structure of the via holes or theplating thickness in the via holes may cause variations in theelectrical resistance or the inductance of the wiring portions.Furthermore, since the substrate material is an organic substance, adielectric constant of the printed circuit board is large, so that it isnot suitable to a semiconductor package that requires a high frequencyperformance. In addition to this problem, there is also an electricityand moisture resistance-related problem in that a water content entersthe inside from the outside via the via holes and corrodes the copperfoil layer in the upper electrode pad portion of the printed circuitboard to which the connecting members such as wire are connected.

[0017] Furthermore, the printed circuit board is made of glass epoxy, sothat this is insulative with respect to thermal conduction. This causesa heat-related problem as well. More specifically, when a semiconductorelement having high power consumption is mounted on the printed circuitboard, heat is not released sufficiently, so that the temperatureincreases in the principal surface on which an integrated circuit isformed in the semiconductor element. As a result, the temperature in theprincipal surface exceeds the allowable temperature, which leads tomalfunction of the circuit.

SUMMARY OF THE INVENTION

[0018] Therefore, with the foregoing in mind, it is a main object of thepresent invention to provide a semiconductor device employing a circuitboard that has good electrical and thermal characteristics and a methodfor producing such a semiconductor device.

[0019] A semiconductor device of the present invention includes acircuit board; a semiconductor element that is mounted on an uppersurface of the circuit board and has an electrode terminal; and asealing resin for sealing a periphery of the semiconductor element thatis mounted on the upper surface of the circuit board. The circuit boardincludes a plurality of conductive members and an insulating substancefor binding and fixing the plurality of conductive members to eachother. Each of the plurality of conductive members includes a conductivematerial formed integrally from the upper surface through the lowersurface of the circuit board, and an insulating material covering anouter circumference of the conductive material. The conductive materialof at least one conductive member of the plurality of conductive membersis exposed to the upper surface of the, circuit board. The electrodeterminal of the semiconductor element is electrically connected to theconductive material of the conductive member exposed to the uppersurface of the circuit board via a connecting member.

[0020] In one embodiment of the present invention, a bonding pad made ofa metal coating film connected to the conductive material of a part ofthe plurality of conductive members, and an electrode pad connected tothe conductive material of a part of the plurality of conductive membersare provided on the upper surface of the circuit board. Thesemiconductor element is mounted on the bonding pad. The electrodeterminal of the semiconductor element is connected to the electrode padvia the connecting member. A lower electrode pad corresponding to theelectrode pad on the upper surface is provided on a lower surface of thecircuit board. The lower electrode pad is connected to the conductivematerial of the conductive member connected to the electrode padprovided on the upper surface.

[0021] It is preferable that the conductive material of at least oneconductive member of the plurality of conductive members is exposed tothe lower surface of the circuit board, and a ball electrode or aprotruding electrode is connected to the conductive material of theconductive member exposed to the lower surface of the circuit board.

[0022] In one embodiment of the present invention, the conductivematerial is a fine line-like conductive material.

[0023] In one embodiment of the present invention, the conductivematerial has a cross-sectional shape of a circle or a polygon.

[0024] In one embodiment of the present invention, the conductive memberand the insulating substance are exposed alternately to a side surfaceof the circuit board.

[0025] It is preferable that the circuit board is an anisotropicconductive circuit board that has electrical conductivity with respectto the upper and the lower surfaces and is electrically insulated in ahorizontal direction.

[0026] In one embodiment of the present invention, a shape of thecircuit board viewed from the upper surface thereof is any one of acircle, a rectangle, a hexagon and an octagon.

[0027] In one embodiment of the present invention, the connecting memberis a conductive metal fine line or a metal ribbon.

[0028] In one embodiment of the present invention, the connecting memberis a conductive protruding electrode.

[0029] A method for producing a semiconductor device of the presentinvention includes the steps of: (a) bundling and arranging a pluralityof conductive members, each of which includes fine line-like conductivematerials whose outer circumference is covered with an insulatingmaterial to form a conductive member cluster; (b) attaching and fixingthe conductive members constituting the conductive member cluster toeach other with an insulative resin to form a rectangular solidsubstrate block; (c) slicing the substrate block with a predeterminedthickness to form a substrate element in which cross-sections of theplurality of conductive materials and the insulating materials coveringthe outer circumferences of the corresponding conductive materials arearranged and whose periphery is made of the insulating resin and theplurality of conductive members; (d) forming metal coating films on anupper surface and a lower surface of the substrate element, therebyforming a circuit board; (e) mounting a semiconductor element having anelectrode terminal on an upper surface of the circuit board; (f)electrically connecting the electrode terminal of the semiconductorelement mounted on the circuit board and the conductive materialpositioned on the upper substrate of the circuit board with a connectingmember; and (g) sealing a periphery of the semiconductor element mountedon the upper surface of the circuit board and the connecting member witha sealing resin.

[0030] In one embodiment of the present invention, in the step (C),slicing is performed at an angle between 300 to 150° with respect to thelongitudinal direction of the conductive member cluster constituting thesubstrate block such that a thickness becomes 0.05 mm to 3.00 mm.

[0031] It is preferable that the method for producing a semiconductordevice further includes performing surface-processing by polishing bothsurfaces of the sliced substrate element, after the step (c).

[0032] In one embodiment of the present invention, the step (d) includesforming a metal coating film in a portion on the upper surface of thesubstrate element on which the semiconductor element is to be mounted toform a bonding pad portion; forming a metal coating film as an electrodepad connected to the conductive material of the substrate element in aportion of the upper surface of the substrate element to which aconnecting member for electrically connecting to the electrode terminalof the semiconductor element to be mounted is to be connected, andforming a metal coating film on the conductive material exposed on thelower surface of the substrate element to form an electrode pad.

[0033] It is preferable that in the step (a), a plurality of conductivemembers are bundled and arranged in a plurality of rows such that theyare densely filled in a grid or staggered manner in cross-section.

[0034] In one embodiment of the present invention, in the step (f), theconnection is performed using a conductive metal fine line as theconnecting member.

[0035] In one embodiment of the present invention, in the step (f), theconnection is performed using a conductive protruding electrode as theconnecting member.

[0036] In one embodiment of the present invention, the method forproducing a semiconductor device further includes forming a ballelectrode or a protruding electrode on an electrode pad on theconductive material exposed on the lower surface of the circuit board,after the step (g).

[0037] In one embodiment of-the present invention, in the step (a), theconductive material is a metal fine line made of at least one selectedfrom the group consisting of copper, a copper alloy, aluminum, analuminum alloy, nickel, and a nickel alloy.

[0038] A circuit board of the present invention includes a plurality ofconductive member; an insulating substance for binding and fixing theplurality of conductive members to each other; wherein each of theplurality of conductive members include a conductive material formedintegrally from one end through the other end and an insulating materialfor covering an outer circumference of the conductive material, andthere is a difference in conductivity between a direction to which theconductive material extends and directions other than that.

[0039] According to the present invention, a semiconductor element ismounted on the upper surface of a circuit board obtained by binding andfixing a plurality of conductive members, each of which includes aconductive material formed integrally from the upper surface through thelower surface of the circuit board, using an insulative substance.Therefore, the electrical resistance and the inductance between theupper and the lower surfaces of the board are significantly small, sothat an electrically and thermally excellent semiconductor device can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIGS. 1A to 1G are views illustrating a method for producing ananisotropic conductive circuit board used in a semiconductor device ofEmbodiment 1 of the present invention.

[0041]FIGS. 2A to 2G are views illustrating a semiconductor device ofEmbodiment 1 of the present invention and a method for producing thesemiconductor device.

[0042]FIG. 3 is a cross-sectional view schematically showing asemiconductor device of Embodiment 2 of the present invention.

[0043]FIGS. 4A to 4C are views illustrating a printed circuit board ofthe semiconductor device of Embodiment 2 of the present invention.

[0044]FIG. 5 is a view showing the substrate mounting state of thesemiconductor device of Embodiment 2 of the present invention.

[0045]FIG. 6 is a cross-sectional view schematically showing asemiconductor device of Embodiment 3 of the present invention.

[0046]FIG. 7 is a cross-sectional view schematically showing asemiconductor device of Embodiment 4 of the present invention.

[0047]FIGS. 8A to 8E are views illustrating a method for producing aconventional semiconductor device.

DETAILED DESCRIPTION OF THE INVENTION

[0048] Hereinafter, embodiments of the present invention will bedescribed with reference of the accompanying drawings. In the followingdrawings, for the sake of simplification of description, the componentshaving substantially the same function bear the same numbers. Thepresent invention is not limited to the following embodiments.Embodiment 1

[0049] First, an embodiment of a circuit board included in asemiconductor device of Embodiment 1 of the present invention will bedescribed.

[0050] In the circuit board of this embodiment, a plurality ofconductive members, each of which include a conductive materialintegrally formed from one end through the other end and an insulatingmaterial covering the outer circumference of the conductive material,are bundled and arranged, and attached and fixed to each other with aninsulative substance, and this circuit board is an anisotropicconductive circuit board having a difference in the conductivity betweenthe direction to which the conductive material is extending and theother directions. In other words, the circuit board of this embodimentis an anisotropic conductive circuit board that includes a plurality ofconductive members, each of which includes a conductive material formedintegrally from the upper surface through the lower surface and coveredwith an insulating material in its outer circumference, and aninsulative resin for binding and fixing the plurality of conductivemembers. The anisotropic conductive circuit board is provided withelectrode pads and at least one bonding pad on the surface of theconductive material of the conductive member exposed to its uppersurface.

[0051]FIG. 1A to 1G are views illustrating a method for producing theanisotropic conductive circuit board of this embodiment.

[0052] First, as shown in a perspective partial view of FIG. 1A, aconductive material 11 that is a component of the circuit board isprepared. The conductive material 11 is made of a conductive metal suchas copper (Cu), a copper alloy, aluminum (Al), an aluminum alloy, nickel(Ni), a nickel alloy, or gold (Au). In this embodiment, as shown in FIG.1A, the conductive material 11 is a wire (metal fine line) having across-sectional shape of a circle (i) or a polygon (hexagon (ii),rectangle (iii), triangle (iv), etc.), and made of a material ofthermally and electrically good conductor such as copper or othermetals. The diameter of the wire of the conductive material 11 is forexample, 10 to 500 μM.

[0053] Next, as shown in a perspective partial view of FIG. 1B, aninsulative substance such as a polyimide resin, a polybenzoxazole resin,an epoxy resin, and enamel is provided around the outer circumference ofthe conductive material 11, so that a conductive member 13 provided withan insulating coating material 12 (insulating material) can be obtained.The insulating coating material (insulating material) 12 is formed byheating so as to be cured after the insulative substance is applied. Theinsulating coating material 12 is formed so as to have a thickness of 1to 100 μm after heating for curing. The curing is performed at atemperature required to cure the materials. In FIG. 1B, the conductivemembers 13 produced with the conductive material 11 having across-sectional shape of a circle (i) or a polygon (hexagon (ii),rectangle (iii), triangle (iv), etc.) as in FIG. 1A are shown, forexample.

[0054] Next, as shown in a perspective partial view of FIG. 1C, aplurality of conductive members 13 are bound so that the cross sectionsof the plurality of conductive members 13 are densely filled to form aconductive member cluster 14. Here, the plurality of conductive members13 are bundled and arranged in a grid or a staggered arrangement incross-section. In FIG. 1C, a staggered arrangement is used to strengththe binding. In FIG. 1C; the conductive member cluster 14 is formed withthe conductive members 13 each of which includes the conductive material11 having a cross-sectional shape of a circle.

[0055] Then, as shown in a perspective partial view of FIG. 1D, aninsulative adhesive 15 is filled in the gaps in the bound and fixedconductive member cluster 14 for attachment, and is heated and cured toform a substrate block 16. The insulative adhesive 15 is made of aninsulative substance such as a polyimide resin, a polybenzoxazole resin,an epoxy resin, and enamel. The curing of the insulative adhesive 15 isperformed at a temperature required to cure the materials.

[0056] Then, as shown in a plan view of FIG. 1E, the substrate block 16formed in the previous process is subjected to slicing processing so asto be cut, for example, along line B-B1 to form an anisotropicconductive original substrate 17 (substrate element). The slicingprocessing is performed at an arbitrary angle between 30° to 150°(typically 90°) with respect to the direction to which the conductivemember 13 (or the conductive material 11) extends (longitudinaldirection) such that the thickness becomes 0.05 mm to 3.00 mm (or 0.05to 2.00 mm). In the slicing processing, the substrate block 16 is cut toa predetermined thickness with a slicing saw or a wire saw. The roughupper and lower surfaces (front surface and back face) of the slicedsubstrate are ground or polished so that they become smooth. There wouldbe no problem if the rough surfaces are provided with a polished finishby, for example, polishing.

[0057] Then, as shown in a plan view of FIG. 1F, a plurality of upperbonding pads 18 a, and a plurality of upper electrode pads 19 asurrounding the upper bonding pads 18 a are formed on the upper surface(front face) of the anisotropic conductive original substrate 17 whoseupper and lower surfaces are smooth. Here, a pattern group including theplurality of bonding pads and electrode pads is arranged repeatedly at apredetermined interval on the entire surface of the anisotropicconductive original substrate 17. That is to say, the upper bonding pads18 a and the upper electrode pads 19 a are formed for each regionsegmented to have a desired area corresponding to a single substrateunit. Although not shown in FIG. 1F, a plurality of lower bonding padsand a plurality of lower electrode pads surrounding the lower bondingpads are formed on the lower surface (back face) of the anisotropicconductive original substrate 17 in the portion corresponding to therespective pads arranged on the upper surface.

[0058] The patterns of the plurality of bonding pad, the electrode padsor the like are formed in the following manner. First, laminated filmsof Cu/Ni/Au are formed on the upper and the lower surfaces of theanisotropic conductive original substrate 17. Then, patterning isperformed to this laminated film with a photomask provided with apredetermined pattern by photolithography so that the upper bonding pads18 a and the plurality of upper electrode pads 19 a surrounding them,and the lower bonding pads and the plurality of lower electrode padssurrounding them are arranged. Thus, the patterns of the plurality ofbonding pad, the electrode pads or the like are formed.

[0059] The laminated coating film of Cu/Ni/Au of this embodiment is amultilayered film in which a Cu layer, a Ni layer and a Au layer arelaminated in this order from the bottom to have a thickness of 14 μm, 4μm, and 0.5 μm, respectively. For this laminated metal coating film, inaddition to the above-described materials, any other material can beused, as long as it is a thermally and electrically good conductor, andthere is no limitation regarding the thickness. Photolithography is atechnique in which a predetermined pattern is formed on a photoresistwith a photomask, and pattern openings are etched by dry or wet etchingso that the bonding pads and the electrode pads are formed.

[0060] Thus, a group of anisotropic conductive circuit boards havingexcellent electrical characteristics in which the upper surfaces of thecircuit boards are connected to the lower surfaces in the shortestdistance can be obtained. Finally, as shown in the plan view of FIG. 1G,the formed group of anisotropic conductive circuit boards is cut at apredetermined line with, for example, a dicing saw or a wire saw, sothat an individually segmented single anisotropic conductive circuitboard 20 can be obtained.

[0061] The obtained anisotropic conductive circuit board 20 include theconductive members constituted by the conductive materials 11 formedintegrally from the upper surface through the lower surface and theinsulating coating films 12 covering the outer circumferences of theconductive materials 11, and the insulative adhesive 15 for binding andfixing the plurality of conductive members 13 to each other. The upperbonding pad 18 a and the plurality of upper electrode pads 19 a areformed on the upper surface of the board 20, and the lower bonding padand the plurality of lower electrode pads (terminal pads) constitutingexternal terminals are formed on the lower surface of the board 20. Withthis structure, the conductive member 13 including the conductivematerial 11 can connect the upper surface to the lower surface of theboard in the shortest distance, so that the electrical resistance andthe inductance between the upper and the lower surfaces of the board canbe reduced significantly. As a result, an anisotropic conductive circuitboard having excellent electrical characteristics can be achieved.

[0062] In addition, the anisotropic conductive circuit board 20 of thisembodiment is not provided with via holes, so that the problem thatvariations in the electrical resistance or the inductance in the circuitportion are caused by variations in the structure of the via holes orplating thickness in the via holes can be avoided. The electricity andmoisture-resistance-related problem that the water content may enter theinside of a printed circuit board from the outside via the via holes,which corrodes the copper foils on the upper electrodes of the printedcircuit board to which a connecting member such as a wire is connectedalso can be avoided. Furthermore, the conductive material 11 formedintegrally from the upper surface through the lower surface of the board20 is made of a substance that is not only electrically but alsothermally good conductor, so that a thermal problem can be suppressed,compared to printed circuit boards made of glass epoxy having poor heatconductivity.

[0063] It should be noted that since the circuit board 20 of thisembodiment is obtained by cutting the group of anisotropic conductivecircuit boards shown in FIG. 1F at a predetermined line, the conductivemember 13 and the insulative adhesive (insulative substance) 15 areexposed alternately on the side of the circuit board 20 of thisembodiment, although this is not shown in FIG. 1G. In FIG. 1G, thecircuit board 20 is a rectangle, but the shape of the circuit board 20can be any one of a circle, a hexagon, and an octagon, in addition to arectangle. Another layer (for example, an insulating layer) can beformed in a portion on the upper and the lower surface of the circuitboard 20 in which the pads (18 and 19) are not positioned. Another layer(for example, an insulating layer) can be formed on the side surface ofthe circuit board 20.

[0064] Next, a semiconductor device and a method for producing thesemiconductor device of this embodiment will be described with referenceto FIGS. 2A to 2G.

[0065]FIGS. 2A to 2G are views illustrating a semiconductor device and amethod for producing the semiconductor device. FIGS. 2A to 2C are a planview, a bottom view and a cross-sectional view of the circuit board 20described above of this embodiment, respectively, and FIGS. 2D to 2G arecross-sectional views showing relevant processes in a production methodof this embodiment.

[0066] First, as shown in FIGS. 2A to 2C, the anisotropic conductivecircuit board 20 of this embodiment is prepared.

[0067] As described with reference to FIGS. 1A to 1G, the anisotropicconductive circuit board 20 of this embodiment includes the plurality ofconductive members 13 and the insulative substance (insulative adhesive)15 for binding and fixing the plurality of conductive members 13 to eachother, and each of the conductive members 13 includes the conductivematerial 11 integrally formed from one end to the other end (i.e., fromthe upper surface through the lower surface of the substrate 20) and aninsulating material 12 (insulating coating material) covering the outercircumference of the conductive material 11. In other words, the circuitboard of this embodiment is constituted with conductive member clustersincluding the plurality of conductive members 13, each of which includesthe conductive material 11 whose outer circumference is covered with theinsulating coating material 12, and the insulative adhesive 15 forbinding and fixing the plurality of conductive members 13. In the upperand the lower surfaces of the substrate 20, the upper bonding pad 18 amade of a metal coating connected to each conductive member 13 of theconductive member cluster and the lower bonding pad 18 b, and the upperelectrode pads 19 a connected to the conductive member of the conductivemember cluster and the lower electrode pads 19 b are provided,respectively. In FIGS. 2A to 2C, a single anisotropic conductive circuitboard 20 is prepared, but in an actual production process, it ispreferable to prepare a substrate in which a plurality of anisotropicconductive circuit boards 20 having the structure as shown in thedrawings are arranged in a matrix and handle this substrate. This ispreferable because if the substrate in which a plurality of anisotropicconductive circuit boards 20 are arranged is used, it is possible toproduce a plurality of semiconductor devices of this embodiment in oneprocess. However, as shown in FIG. 2A to 2C, one anisotropic conductivecircuit board 20 is prepared and then a semiconductor device may beproduced with it.

[0068] Next, as shown in FIG. 2D, a die bonding process is performed.First, a suitable amount of a conductive adhesive 21 such as Ag pastecontaining a mixture of an epoxy resin and Ag flakes is dripped forapplication onto the surface of the upper bonding pad 18 a on the uppersurface of the anisotropic conductive circuit board 20. Then, asemiconductor element 22 is mounted on the conductive adhesive 21 on theupper bonding pad 18 a with the principal surface of the circuit upward.Therefore, heating is performed in a curing furnace at 100 to 250° C. ina no-noxidation atmosphere (e.g., nitrogen atmosphere) for one to twohours, so that the semiconductor element 22 is attached and fixed ontothe upper bonding pad 18 a with the conductive adhesive 21. In thiscase, solders can be used as the conductive adhesive 21, or when thecuring temperature of the conductive adhesive 21 is low, heating can beperformed in the air.

[0069] Then, as shown in FIG. 2E, a wire bonding process is performed.First, a plurality of electrode terminals (not shown) arranged in theprincipal surface of the semiconductor element 22 mounted on the board20 are connected to the plurality of upper electrode pads 19 a arrangedin the periphery of the upper bonding pad on the upper surface of theanisotropic conductive circuit board 20 with connecting members 23 madeof fine lines of Au, Cu, Al or the like, using a wire bonder. Thediameter of the fine line is for example, 15 to 35 μm. Wire bonding isperformed at a temperature between 150 to 250° C. under a necessary loadfor connection for a necessary period of time in a nitrogen atmospherewhile applying ultrasonic vibrations. However, if the temperature is200° C. or less, wire bonding can be performed in the air. In thisembodiment, metal fine lines are used as the connecting member 23, butmetal ribbons can be used as well.

[0070] Then, as shown in FIG. 2F, a resin sealing process is performed.More specifically, the wire-bonded anisotropic conductive circuit board20 is set in a resin sealing mold, and then a transfer resin sealing isperformed in which a melted epoxy resin is pored into the mold cavityfrom a gate port of the resin sealing mold, so that a sealing resin 24is formed on the upper surface of the board. Here, the surfacetemperature of the resin sealing mold for molding is 170 to 190° C., andthe mold cavity can be such that the entire upper surface of theanisotropic conductive circuit board 20 is covered. Thus, asemiconductor device 25 having the anisotropic conductive circuit board20 of this embodiment is obtained.

[0071] Thereafter, as shown in FIG. 2G, a secondary mounting process maybe performed in which the semiconductor device is mounted on a mountingcircuit board (mounting substrate) such as a mother board. Thesemiconductor device 25 have the lower bonding pad 18 b and the lowerelectrode pads 19 b on the lower surface of the board 20 attached andfixed to the semiconductor element 22, and therefore the semiconductordevice 25 can be fixed on a predetermined position of a mounting circuitboard 26 in the following manner: The lower bonding pad 18 b and thelower electrode pads 19 b provided in the board 20 of the semiconductordevice are arranged so as to correspond to the portions in which solderpaste 28 is printed by a solder printing technique in the region on thecircuit terminals 27 provided on the mounting circuit board 26.Thereafter, the solder paste 28 is melted in a reflow furnace. Thus, amounted structure in which the secondary mounting is completed can beobtained.

[0072] As describe above, the semiconductor device 25 including theanisotropic conductive circuit board 20, the semiconductor element 22mounted on the upper surface of the anisotropic conductive circuit board20, the connecting members 23 electrically connecting the electrodeterminals of the semiconductor element 22 and the upper electrode pads19 a exposed on the upper surface of the anisotropic conductive circuitboard 20, and the sealing resin 24 sealing the periphery of thesemiconductor element 22 on the upper surface of the anisotropicconductive circuit board 20 and the connecting members 23 can beachieved. The semiconductor device 25 of this embodiment constitutes apackage by utilizing the above-described anisotropic conductive circuitboard 20 as the circuit board, unlike a conventional LGA (or BGA) typepackage employing a printed circuit board, and therefore thesemiconductor device is electrically, moisture-resistantly and thermallyexcellent.

[0073] In other words, the semiconductor device of this embodiment ofthe present invention includes, as a component, the anisotropicconductive circuit board obtained by bundling a plurality of conductivemembers, each of which includes a fine line-like conductive materialcovered with an insulating material, to form a block with an insulativeadhesive and slicing the block. Therefore, the electrical resistance andthe inductance between the upper and the lower surfaces of the board aresignificantly small, and an electrically excellent semiconductor devicecan be achieved. Furthermore, since the board itself does not includevia holes, unlike conventional boards, so that water hardly goes intothe upper surface of the board, and therefore a semiconductor devicehaving high reliability can be achieved. In addition, since the board ismade of a good conductor, the heat release properties to the secondarymounting substrate are improved significantly, so that a semiconductordevice that is electrically, moisture-resistantly and thermallyexcellent can be provided.

[0074] Furthermore, in the method for producing the semiconductor deviceof this embodiment of the present invention, a plurality of conductivemembers, each of which includes a fine line-like conductive materialcovered with an insulating coating are bundled to form a block with aninsulative adhesive and the block is sliced to form an anisotropicconductive circuit board, and a semiconductor device is produced, usingthat board. Therefore, a semiconductor device that is electrically,moistureresistantly and thermally excellent can be produced.

Embodiment 2

[0075] Embodiment 2 of the present invention will be described withreference to FIGS. 3 to 5. FIG. 3 is a schematic view showing thestructure of the semiconductor device of Embodiment 2.

[0076] The semiconductor device of this embodiment shown in FIG. 3 isdifferent from the semiconductor device of Embodiment 1 in that aplurality of rows (two rows) of lower electrode pads 19 b are aligned.Other aspects are the same as in Embodiment 1. For the sake ofsimplification of description, in this embodiment and the followingembodiments, different aspects from those of Embodiment 1 are mainlydescribed and other aspects will be omitted or simplified.

[0077] The semiconductor device shown in FIG. 3 includes an anisotropicconductive circuit board 20 including an upper bonding pad 18 a, a lowerbonding pad 18 b, a plurality of upper electrode pads 19 a and aplurality of lower electrode pads 19 b that are aligned in a pluralityof rows (two rows) on the upper and the lower surfaces thereof, asemiconductor element 22 mounted on the upper surface of the anisotropicconductive circuit board 20 with a conductive adhesive, connectingmembers 23 for electrically connecting the electrode terminals of thesemiconductor element 22 and the upper electrode pad 19 a exposed on theupper surface of the anisotropic conductive circuit board 20, and asealing resin 24 for sealing the periphery of the semiconductor element22 on the anisotropic conductive circuit board 20 and the connectingmembers 23.

[0078] In the semiconductor device of this embodiment, as shown in FIGS.4A to 4C, a plurality of rows of the upper electrode pads 19 a and lowerelectrode pads 19 b are provided, instead of the one row structure shownin FIGS. 2A to 2G, on the anisotropic conductive circuit board 20. Thissemiconductor can be produced in the same manner as in Embodiment 1,except for forming an increased number of terminals.

[0079] As shown in FIG. 5, a BGA type semiconductor device can beachieved by providing ball electrodes 29 such as metal solder balls tothe upper bonding pad 18 b and the lower electrode pads 19 b on theanisotropic conductive circuit board 20. FIG. 5 shows the state wherethe ball the semiconductor device is mounted on the mounting substratevia the ball electrodes.

Embodiment 3

[0080] Next, Embodiment 3 will be described with reference to FIG. 6.FIG. 6 is a schematic view showing the cross-sectional structure of asemiconductor device of Embodiment 3.

[0081] The semiconductor device shown in FIG. 6 includes an anisotropicconductive circuit board 20 including a lower bonding pad 18 b, aplurality of upper electrode pads 19 a and lower electrode pads 19 b onthe upper and the lower surfaces thereof, a semiconductor element 22mounted on the upper surface of the anisotropic conductive circuit board20 with a conductive adhesive by flip-chip mounting, protrudingelectrodes 30 that are connecting members for electrically connectingthe electrode terminals of the semiconductor element 22 and the upperelectrode pad 19 a. Furthermore, a sealing resin 24 (underfill material)seals the gap between the upper surface of the anisotropic conductivecircuit board 20 and the semiconductor element 22.

[0082] The semiconductor device of this embodiment has a flip-chipmounting structure in which the semiconductor element is mounted on thesubstrate such that the principal surface side in which a circuit isformed is opposed to the substrate, and is connected to the substratewith the protruding electrodes without using metal fine lines as theconnecting members, so that a CSP (chip size package) type semiconductordevice having the same size for the substrate and the semiconductorelement can be realized. In the production of this type of semiconductordevice, it is not necessary to provide the upper bonding pads on theupper surface of the anisotropic conductive circuit board to be used.

Embodiment 4

[0083] Next, Embodiment 4 will be described with reference to FIG. 7.FIG. 7 is a schematic view showing the cross-sectional structure of asemiconductor device of Embodiment 4.

[0084] The semiconductor device shown in FIG. 7 includes an anisotropicconductive circuit board 20 including a plurality of upper electrodepads 19 a and lower electrode pads 19 b on the upper and the lowersurfaces thereof, a semiconductor element 22 mounted on the uppersurface of the anisotropic conductive circuit board 20 with a conductiveadhesive by flip-chip mounting, protruding electrodes 30 (bumpelectrodes) that are connecting members for electrically connecting theelectrode terminals of the semiconductor element 22 and the uppercorresponding electrode pad 19 a, and a sealing resin 24 (underfillmaterial) for sealing the gap between the upper surface of theanisotropic conductive circuit board 20 and the semiconductor element22.

[0085] The semiconductor device of this embodiment has a flip-chipmounting structure in which the semiconductor element is mounted on thesubstrate such that the principal surface side in which a circuit isformed is opposed to the substrate, and is connected to the substratewith the protruding electrodes without using metal fine lines as theconnecting members, so that a CSP (chip size package) type semiconductordevice having the same size for the substrate and the semiconductorelement can be realized. In the production of this type of semiconductordevice, it is not necessary to provide the bonding pads for mounting thesemiconductor device on the upper and the lower surfaces of theanisotropic conductive circuit board to be used.

[0086] Furthermore, in the semiconductor device shown in FIG. 7, an areaarray pad type of semiconductor element in which electrode terminals areformed in an array manner on the principal surface of the semiconductorelement 22 is used as the semiconductor element 22 to be mounted. Alsofor the semiconductor device of this embodiment, a CSP structure can berealized as for the semiconductor device shown in FIG. 6.

[0087] In both the semiconductor devices shown in FIGS. 6 and 7, therewould be no problem if ball elements are provided on the lower electrodepads on the lower surface of the board to constitute a BGA typesemiconductor device.

[0088] The semiconductor devices of the above-described embodimentsincludes, as a component, an anisotropic conductive circuit boardobtained by bundling a plurality of conductive members including fineline-like conductive materials covered with insulating coating to formsa block with an insulative adhesive, and slicing the block. Therefore,the electrical resistance and the inductance between the upper and thelower surfaces of the board are significantly small. Furthermore, sincethe board itself does not include via holes, unlike conventional boards,so that water hardly goes into the upper surface of the board, andtherefore a semiconductor device having high reliability can beachieved. In addition, since the board is made of a good conductor, theheat release properties to a secondary mounting substrate are improvedsignificantly, so that a semiconductor device that is electrically,moisture-resistantly and thermally excellent can be provided.

[0089] The invention may be embodied in other forms without departingfrom the spirit or essential characteristics thereof. The embodimentsdisclosed in this application are to be considered in all respects asillustrative and not limiting. The scope of the invention is indicatedby the appended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A method for producing a semiconductor devicecomprising the steps of: (a) bundling and arranging a plurality ofconductive members, each of which includes fine line-like conductivematerials whose outer circumference is covered with an insulatingmaterial to form a conductive member cluster; (b) attaching and fixingthe conductive members constituting the conductive member cluster toeach other with an insulative resin to form a rectangular solidsubstrate block; (c) slicing the substrate block with a predeterminedthickness to form a substrate element in which cross-sections of theplurality of conductive materials and the insulating materials coveringthe outer circumferences of the corresponding conductive materials arearranged and whose periphery is made of the insulating resin and theplurality of conductive members; (d) forming metal coating films on anupper surface and a lower surface of the substrate element, therebyforming a circuit board; (e) mounting a semiconductor element having anelectrode terminal on an upper surface of the circuit board; (f)electrically connecting the electrode terminal of the semiconductorelement mounted on the circuit board and the conductive materialpositioned on the upper substrate of the circuit board with a connectingmember; and (g) sealing a periphery of the semiconductor element mountedon the upper surface of the circuit board and the connecting member witha sealing resin.
 2. The method for producing a semiconductor deviceaccording to claim 1, wherein in the step (C), slicing is performed atan angle between 30° to 150° with respect to the longitudinal directionof the conductive member cluster constituting the substrate block suchthat a thickness becomes 0.05 mm to 3.00 mm.
 3. The method for producinga semiconductor device according to claim 1, further comprisingperforming surface-processing by polishing both surfaces of the slicedsubstrate element, after the step (c).
 4. The method for producing asemiconductor device according to claim 1, wherein the step (d)comprises: forming a metal coating film in a portion on the uppersurface of the substrate element on which the semiconductor element isto be mounted to form a bonding pad portion; forming a metal coatingfilm as an electrode pad connected to the conductive material of thesubstrate element in a portion of the upper surface of the substrateelement to which a connecting member for electrically connecting to theelectrode terminal of the semiconductor element to be mounted is to beconnected, and forming a metal coating film on the conductive materialexposed on the lower surface of the substrate element to form anelectrode pad.
 5. The method for producing a semiconductor deviceaccording to claim 1, wherein in the step (a), a plurality of conductivemembers are bundled and arranged in a plurality of rows such that theyare densely filled in a grid or staggered manner in cross-section. 6.The method for producing a semiconductor device according to claim 1,wherein in the step (f), the connection is performed using a conductivemetal fine line as the connecting member.
 7. The method for producing asemiconductor device according to claim 1, wherein in the step (f), theconnection is performed using a conductive protruding electrode as theconnecting member.
 8. The method for producing a semiconductor deviceaccording to claim 1, further comprising forming a ball electrode or aprotruding electrode on an electrode pad on the conductive materialexposed on the lower surface of the circuit board, after the step (g).9. The method for producing a semiconductor device according to claim 1,wherein in the step (a), the conductive material is a metal fine linemade of at least one selected from the group consisting of copper, acopper alloy, aluminum, an aluminum alloy, nickel, and a nickel alloy.